My 1964 Farmall Cub is running rough and looses power when placed in load (up a hill or with plow in ground). The carburetor's discharge tube is broken off above the threads. Would this cause the problem and if so can you only buy that part?

I'm assuming the broken carburetor piece is the idle tube, a thin brass tube threaded in the top casting that protrudes into the bottom casting. It should not affect full power performance. A broken fuel discharge tube will affect performance, the discharge tube is the brass tube that sticks up into the venturi.

Perform a full tune up, including valve adjustment and compression check. Many performance issues blamed on the carburetor are actually ignition and mechanical problems. Always attack the carburetor last!

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Lurker Carl wrote:I'm assuming the broken carburetor piece is the idle tube, a thin brass tube threaded in the top casting that protrudes into the bottom casting. It should not affect full power performance. A broken fuel discharge tube will affect performance, the discharge tube is the brass tube that sticks up into the venturi.

While I never tried to see if the Cub would run with a broken discharge tube, I doubt that it would. The venturi would not get a fuel supply. But with broken or missing discharge tube, fuel would run through the carburetor continuously since the base of that tube is lower than the bowl fuel level as normally controlled by the float. So it is possible that the discharge tube and idle tube have been confused in this instance. The idle tube projects downward from the top of the carburetor perpendicular and the discharge tube projects upward from the bottom of the carburetor at an angle.